ssh.c

   1 /* $OpenBSD: ssh.c,v 1.303 2007/09/04 11:15:55 djm Exp $ */
   2 /*
   3  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   4  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   5  *                    All rights reserved
   6  * Ssh client program.  This program can be used to log into a remote machine.
   7  * The software supports strong authentication, encryption, and forwarding
   8  * of X11, TCP/IP, and authentication connections.
   9  *
  10  * As far as I am concerned, the code I have written for this software
  11  * can be used freely for any purpose.  Any derived versions of this
  12  * software must be clearly marked as such, and if the derived work is
  13  * incompatible with the protocol description in the RFC file, it must be
  14  * called by a name other than "ssh" or "Secure Shell".
  15  *
  16  * Copyright (c) 1999 Niels Provos.  All rights reserved.
  17  * Copyright (c) 2000, 2001, 2002, 2003 Markus Friedl.  All rights reserved.
  18  *
  19  * Modified to work with SSL by Niels Provos <provos@citi.umich.edu>
  20  * in Canada (German citizen).
  21  *
  22  * Redistribution and use in source and binary forms, with or without
  23  * modification, are permitted provided that the following conditions
  24  * are met:
  25  * 1. Redistributions of source code must retain the above copyright
  26  *    notice, this list of conditions and the following disclaimer.
  27  * 2. Redistributions in binary form must reproduce the above copyright
  28  *    notice, this list of conditions and the following disclaimer in the
  29  *    documentation and/or other materials provided with the distribution.
  30  *
  31  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  32  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  33  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  34  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  35  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  36  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  37  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  38  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  39  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  40  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  41  */
  42
  43 #include "includes.h"
  44
  45 #include <sys/types.h>
  46 #ifdef HAVE_SYS_STAT_H
  47 # include <sys/stat.h>
  48 #endif
  49 #include <sys/resource.h>
  50 #include <sys/ioctl.h>
  51 #include <sys/socket.h>
  52 #include <sys/un.h>
  53
  54 #include <ctype.h>
  55 #include <errno.h>
  56 #include <fcntl.h>
  57 #include <netdb.h>
  58 #ifdef HAVE_PATHS_H
  59 #include <paths.h>
  60 #endif
  61 #include <pwd.h>
  62 #include <signal.h>
  63 #include <stdarg.h>
  64 #include <stddef.h>
  65 #include <stdio.h>
  66 #include <stdlib.h>
  67 #include <string.h>
  68 #include <unistd.h>
  69
  70 #include <netinet/in.h>
  71 #include <arpa/inet.h>
  72
  73 #include <openssl/evp.h>
  74 #include <openssl/err.h>
  75
  76 #include "xmalloc.h"
  77 #include "ssh.h"
  78 #include "ssh1.h"
  79 #include "ssh2.h"
  80 #include "compat.h"
  81 #include "cipher.h"
  82 #include "packet.h"
  83 #include "buffer.h"
  84 #include "channels.h"
  85 #include "key.h"
  86 #include "authfd.h"
  87 #include "authfile.h"
  88 #include "pathnames.h"
  89 #include "dispatch.h"
  90 #include "clientloop.h"
  91 #include "log.h"
  92 #include "readconf.h"
  93 #include "sshconnect.h"
  94 #include "misc.h"
  95 #include "kex.h"
  96 #include "mac.h"
  97 #include "sshpty.h"
  98 #include "match.h"
  99 #include "msg.h"
 100 #include "monitor_fdpass.h"
 101 #include "uidswap.h"
 102 #include "version.h"
 103
 104 #ifdef SMARTCARD
 105 #include "scard.h"
 106 #endif
 107
 108 extern char *__progname;
 109
 110 /* Flag indicating whether debug mode is on.  This can be set on the command line. */
 111 int debug_flag = 0;
 112
 113 /* Flag indicating whether a tty should be allocated */
 114 int tty_flag = 0;
 115 int no_tty_flag = 0;
 116 int force_tty_flag = 0;
 117
 118 /* don't exec a shell */
 119 int no_shell_flag = 0;
 120
 121 /*
 122  * Flag indicating that nothing should be read from stdin.  This can be set
 123  * on the command line.
 124  */
 125 int stdin_null_flag = 0;
 126
 127 /*
 128  * Flag indicating that ssh should fork after authentication.  This is useful
 129  * so that the passphrase can be entered manually, and then ssh goes to the
 130  * background.
 131  */
 132 int fork_after_authentication_flag = 0;
 133
 134 /*
 135  * General data structure for command line options and options configurable
 136  * in configuration files.  See readconf.h.
 137  */
 138 Options options;
 139
 140 /* optional user configfile */
 141 char *config = NULL;
 142
 143 /*
 144  * Name of the host we are connecting to.  This is the name given on the
 145  * command line, or the HostName specified for the user-supplied name in a
 146  * configuration file.
 147  */
 148 char *host;
 149
 150 /* socket address the host resolves to */
 151 struct sockaddr_storage hostaddr;
 152
 153 /* Private host keys. */
 154 Sensitive sensitive_data;
 155
 156 /* Original real UID. */
 157 uid_t original_real_uid;
 158 uid_t original_effective_uid;
 159
 160 /* command to be executed */
 161 Buffer command;
 162
 163 /* Should we execute a command or invoke a subsystem? */
 164 int subsystem_flag = 0;
 165
 166 /* # of replies received for global requests */
 167 static int client_global_request_id = 0;
 168
 169 /* pid of proxycommand child process */
 170 pid_t proxy_command_pid = 0;
 171
 172 /* fd to control socket */
 173 int control_fd = -1;
 174
 175 /* Multiplexing control command */
 176 static u_int mux_command = 0;
 177
 178 /* Only used in control client mode */
 179 volatile sig_atomic_t control_client_terminate = 0;
 180 u_int control_server_pid = 0;
 181
 182 /* Prints a help message to the user.  This function never returns. */
 183
 184 static void
 185 usage(void)
 186 {
 187         fprintf(stderr,
 188 "usage: ssh [-1246AaCfgKkMNnqsTtVvXxY] [-b bind_address] [-c cipher_spec]\n"
 189 "           [-D [bind_address:]port] [-e escape_char] [-F configfile]\n"
 190 "           [-i identity_file] [-L [bind_address:]port:host:hostport]\n"
 191 "           [-l login_name] [-m mac_spec] [-O ctl_cmd] [-o option] [-p port]\n"
 192 "           [-R [bind_address:]port:host:hostport] [-S ctl_path]\n"
 193 "           [-w local_tun[:remote_tun]] [user@]hostname [command]\n"
 194         );
 195         exit(255);
 196 }
 197
 198 static int ssh_session(void);
 199 static int ssh_session2(void);
 200 static void load_public_identity_files(void);
 201 static void control_client(const char *path);
 202
 203 /*
 204  * Main program for the ssh client.
 205  */
 206 int
 207 main(int ac, char **av)
 208 {
 209         int i, opt, exit_status;
 210         char *p, *cp, *line, buf[256];
 211         struct stat st;
 212         struct passwd *pw;
 213         int dummy, timeout_ms;
 214         extern int optind, optreset;
 215         extern char *optarg;
 216         struct servent *sp;
 217         Forward fwd;
 218
 219         /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
 220         sanitise_stdfd();
 221
 222         __progname = ssh_get_progname(av[0]);
 223         init_rng();
 224
 225         /*
 226          * Save the original real uid.  It will be needed later (uid-swapping
 227          * may clobber the real uid).
 228          */
 229         original_real_uid = getuid();
 230         original_effective_uid = geteuid();
 231
 232         /*
 233          * Use uid-swapping to give up root privileges for the duration of
 234          * option processing.  We will re-instantiate the rights when we are
 235          * ready to create the privileged port, and will permanently drop
 236          * them when the port has been created (actually, when the connection
 237          * has been made, as we may need to create the port several times).
 238          */
 239         PRIV_END;
 240
 241 #ifdef HAVE_SETRLIMIT
 242         /* If we are installed setuid root be careful to not drop core. */
 243         if (original_real_uid != original_effective_uid) {
 244                 struct rlimit rlim;
 245                 rlim.rlim_cur = rlim.rlim_max = 0;
 246                 if (setrlimit(RLIMIT_CORE, &rlim) < 0)
 247                         fatal("setrlimit failed: %.100s", strerror(errno));
 248         }
 249 #endif
 250         /* Get user data. */
 251         pw = getpwuid(original_real_uid);
 252         if (!pw) {
 253                 logit("You don't exist, go away!");
 254                 exit(255);
 255         }
 256         /* Take a copy of the returned structure. */
 257         pw = pwcopy(pw);
 258
 259         /*
 260          * Set our umask to something reasonable, as some files are created
 261          * with the default umask.  This will make them world-readable but
 262          * writable only by the owner, which is ok for all files for which we
 263          * don't set the modes explicitly.
 264          */
 265         umask(022);
 266
 267         /* Initialize option structure to indicate that no values have been set. */
 268         initialize_options(&options);
 269
 270         /* Parse command-line arguments. */
 271         host = NULL;
 272
 273  again:
 274         while ((opt = getopt(ac, av,
 275             "1246ab:c:e:fgi:kl:m:no:p:qstvxACD:F:I:KL:MNO:PR:S:TVw:XY")) != -1) {
 276                 switch (opt) {
 277                 case '1':
 278                         options.protocol = SSH_PROTO_1;
 279                         break;
 280                 case '2':
 281                         options.protocol = SSH_PROTO_2;
 282                         break;
 283                 case '4':
 284                         options.address_family = AF_INET;
 285                         break;
 286                 case '6':
 287                         options.address_family = AF_INET6;
 288                         break;
 289                 case 'n':
 290                         stdin_null_flag = 1;
 291                         break;
 292                 case 'f':
 293                         fork_after_authentication_flag = 1;
 294                         stdin_null_flag = 1;
 295                         break;
 296                 case 'x':
 297                         options.forward_x11 = 0;
 298                         break;
 299                 case 'X':
 300                         options.forward_x11 = 1;
 301                         break;
 302                 case 'Y':
 303                         options.forward_x11 = 1;
 304                         options.forward_x11_trusted = 1;
 305                         break;
 306                 case 'g':
 307                         options.gateway_ports = 1;
 308                         break;
 309                 case 'O':
 310                         if (strcmp(optarg, "check") == 0)
 311                                 mux_command = SSHMUX_COMMAND_ALIVE_CHECK;
 312                         else if (strcmp(optarg, "exit") == 0)
 313                                 mux_command = SSHMUX_COMMAND_TERMINATE;
 314                         else
 315                                 fatal("Invalid multiplex command.");
 316                         break;
 317                 case 'P':       /* deprecated */
 318                         options.use_privileged_port = 0;
 319                         break;
 320                 case 'a':
 321                         options.forward_agent = 0;
 322                         break;
 323                 case 'A':
 324                         options.forward_agent = 1;
 325                         break;
 326                 case 'k':
 327                         options.gss_deleg_creds = 0;
 328                         break;
 329                 case 'K':
 330                         options.gss_authentication = 1;
 331                         options.gss_deleg_creds = 1;
 332                         break;
 333                 case 'i':
 334                         if (stat(optarg, &st) < 0) {
 335                                 fprintf(stderr, "Warning: Identity file %s "
 336                                     "not accessible: %s.\n", optarg,
 337                                     strerror(errno));
 338                                 break;
 339                         }
 340                         if (options.num_identity_files >=
 341                             SSH_MAX_IDENTITY_FILES)
 342                                 fatal("Too many identity files specified "
 343                                     "(max %d)", SSH_MAX_IDENTITY_FILES);
 344                         options.identity_files[options.num_identity_files++] =
 345                             xstrdup(optarg);
 346                         break;
 347                 case 'I':
 348 #ifdef SMARTCARD
 349                         options.smartcard_device = xstrdup(optarg);
 350 #else
 351                         fprintf(stderr, "no support for smartcards.\n");
 352 #endif
 353                         break;
 354                 case 't':
 355                         if (tty_flag)
 356                                 force_tty_flag = 1;
 357                         tty_flag = 1;
 358                         break;
 359                 case 'v':
 360                         if (debug_flag == 0) {
 361                                 debug_flag = 1;
 362                                 options.log_level = SYSLOG_LEVEL_DEBUG1;
 363                         } else {
 364                                 if (options.log_level < SYSLOG_LEVEL_DEBUG3)
 365                                         options.log_level++;
 366                                 break;
 367                         }
 368                         /* FALLTHROUGH */
 369                 case 'V':
 370                         fprintf(stderr, "%s, %s\n",
 371                             SSH_RELEASE, SSLeay_version(SSLEAY_VERSION));
 372                         if (opt == 'V')
 373                                 exit(0);
 374                         break;
 375                 case 'w':
 376                         if (options.tun_open == -1)
 377                                 options.tun_open = SSH_TUNMODE_DEFAULT;
 378                         options.tun_local = a2tun(optarg, &options.tun_remote);
 379                         if (options.tun_local == SSH_TUNID_ERR) {
 380                                 fprintf(stderr, "Bad tun device '%s'\n", optarg);
 381                                 exit(255);
 382                         }
 383                         break;
 384                 case 'q':
 385                         options.log_level = SYSLOG_LEVEL_QUIET;
 386                         break;
 387                 case 'e':
 388                         if (optarg[0] == '^' && optarg[2] == 0 &&
 389                             (u_char) optarg[1] >= 64 &&
 390                             (u_char) optarg[1] < 128)
 391                                 options.escape_char = (u_char) optarg[1] & 31;
 392                         else if (strlen(optarg) == 1)
 393                                 options.escape_char = (u_char) optarg[0];
 394                         else if (strcmp(optarg, "none") == 0)
 395                                 options.escape_char = SSH_ESCAPECHAR_NONE;
 396                         else {
 397                                 fprintf(stderr, "Bad escape character '%s'.\n",
 398                                     optarg);
 399                                 exit(255);
 400                         }
 401                         break;
 402                 case 'c':
 403                         if (ciphers_valid(optarg)) {
 404                                 /* SSH2 only */
 405                                 options.ciphers = xstrdup(optarg);
 406                                 options.cipher = SSH_CIPHER_INVALID;
 407                         } else {
 408                                 /* SSH1 only */
 409                                 options.cipher = cipher_number(optarg);
 410                                 if (options.cipher == -1) {
 411                                         fprintf(stderr,
 412                                             "Unknown cipher type '%s'\n",
 413                                             optarg);
 414                                         exit(255);
 415                                 }
 416                                 if (options.cipher == SSH_CIPHER_3DES)
 417                                         options.ciphers = "3des-cbc";
 418                                 else if (options.cipher == SSH_CIPHER_BLOWFISH)
 419                                         options.ciphers = "blowfish-cbc";
 420                                 else
 421                                         options.ciphers = (char *)-1;
 422                         }
 423                         break;
 424                 case 'm':
 425                         if (mac_valid(optarg))
 426                                 options.macs = xstrdup(optarg);
 427                         else {
 428                                 fprintf(stderr, "Unknown mac type '%s'\n",
 429                                     optarg);
 430                                 exit(255);
 431                         }
 432                         break;
 433                 case 'M':
 434                         if (options.control_master == SSHCTL_MASTER_YES)
 435                                 options.control_master = SSHCTL_MASTER_ASK;
 436                         else
 437                                 options.control_master = SSHCTL_MASTER_YES;
 438                         break;
 439                 case 'p':
 440                         options.port = a2port(optarg);
 441                         if (options.port == 0) {
 442                                 fprintf(stderr, "Bad port '%s'\n", optarg);
 443                                 exit(255);
 444                         }
 445                         break;
 446                 case 'l':
 447                         options.user = optarg;
 448                         break;
 449
 450                 case 'L':
 451                         if (parse_forward(&fwd, optarg))
 452                                 add_local_forward(&options, &fwd);
 453                         else {
 454                                 fprintf(stderr,
 455                                     "Bad local forwarding specification '%s'\n",
 456                                     optarg);
 457                                 exit(255);
 458                         }
 459                         break;
 460
 461                 case 'R':
 462                         if (parse_forward(&fwd, optarg)) {
 463                                 add_remote_forward(&options, &fwd);
 464                         } else {
 465                                 fprintf(stderr,
 466                                     "Bad remote forwarding specification "
 467                                     "'%s'\n", optarg);
 468                                 exit(255);
 469                         }
 470                         break;
 471
 472                 case 'D':
 473                         cp = p = xstrdup(optarg);
 474                         memset(&fwd, '\0', sizeof(fwd));
 475                         fwd.connect_host = "socks";
 476                         if ((fwd.listen_host = hpdelim(&cp)) == NULL) {
 477                                 fprintf(stderr, "Bad dynamic forwarding "
 478                                     "specification '%.100s'\n", optarg);
 479                                 exit(255);
 480                         }
 481                         if (cp != NULL) {
 482                                 fwd.listen_port = a2port(cp);
 483                                 fwd.listen_host = cleanhostname(fwd.listen_host);
 484                         } else {
 485                                 fwd.listen_port = a2port(fwd.listen_host);
 486                                 fwd.listen_host = NULL;
 487                         }
 488
 489                         if (fwd.listen_port == 0) {
 490                                 fprintf(stderr, "Bad dynamic port '%s'\n",
 491                                     optarg);
 492                                 exit(255);
 493                         }
 494                         add_local_forward(&options, &fwd);
 495                         xfree(p);
 496                         break;
 497
 498                 case 'C':
 499                         options.compression = 1;
 500                         break;
 501                 case 'N':
 502                         no_shell_flag = 1;
 503                         no_tty_flag = 1;
 504                         break;
 505                 case 'T':
 506                         no_tty_flag = 1;
 507                         break;
 508                 case 'o':
 509                         dummy = 1;
 510                         line = xstrdup(optarg);
 511                         if (process_config_line(&options, host ? host : "",
 512                             line, "command-line", 0, &dummy) != 0)
 513                                 exit(255);
 514                         xfree(line);
 515                         break;
 516                 case 's':
 517                         subsystem_flag = 1;
 518                         break;
 519                 case 'S':
 520                         if (options.control_path != NULL)
 521                                 free(options.control_path);
 522                         options.control_path = xstrdup(optarg);
 523                         break;
 524                 case 'b':
 525                         options.bind_address = optarg;
 526                         break;
 527                 case 'F':
 528                         config = optarg;
 529                         break;
 530                 default:
 531                         usage();
 532                 }
 533         }
 534
 535         ac -= optind;
 536         av += optind;
 537
 538         if (ac > 0 && !host && **av != '-') {
 539                 if (strrchr(*av, '@')) {
 540                         p = xstrdup(*av);
 541                         cp = strrchr(p, '@');
 542                         if (cp == NULL || cp == p)
 543                                 usage();
 544                         options.user = p;
 545                         *cp = '\0';
 546                         host = ++cp;
 547                 } else
 548                         host = *av;
 549                 if (ac > 1) {
 550                         optind = optreset = 1;
 551                         goto again;
 552                 }
 553                 ac--, av++;
 554         }
 555
 556         /* Check that we got a host name. */
 557         if (!host)
 558                 usage();
 559
 560         SSLeay_add_all_algorithms();
 561         ERR_load_crypto_strings();
 562
 563         /* Initialize the command to execute on remote host. */
 564         buffer_init(&command);
 565
 566         /*
 567          * Save the command to execute on the remote host in a buffer. There
 568          * is no limit on the length of the command, except by the maximum
 569          * packet size.  Also sets the tty flag if there is no command.
 570          */
 571         if (!ac) {
 572                 /* No command specified - execute shell on a tty. */
 573                 tty_flag = 1;
 574                 if (subsystem_flag) {
 575                         fprintf(stderr,
 576                             "You must specify a subsystem to invoke.\n");
 577                         usage();
 578                 }
 579         } else {
 580                 /* A command has been specified.  Store it into the buffer. */
 581                 for (i = 0; i < ac; i++) {
 582                         if (i)
 583                                 buffer_append(&command, " ", 1);
 584                         buffer_append(&command, av[i], strlen(av[i]));
 585                 }
 586         }
 587
 588         /* Cannot fork to background if no command. */
 589         if (fork_after_authentication_flag && buffer_len(&command) == 0 && !no_shell_flag)
 590                 fatal("Cannot fork into background without a command to execute.");
 591
 592         /* Allocate a tty by default if no command specified. */
 593         if (buffer_len(&command) == 0)
 594                 tty_flag = 1;
 595
 596         /* Force no tty */
 597         if (no_tty_flag)
 598                 tty_flag = 0;
 599         /* Do not allocate a tty if stdin is not a tty. */
 600         if ((!isatty(fileno(stdin)) || stdin_null_flag) && !force_tty_flag) {
 601                 if (tty_flag)
 602                         logit("Pseudo-terminal will not be allocated because stdin is not a terminal.");
 603                 tty_flag = 0;
 604         }
 605
 606         /*
 607          * Initialize "log" output.  Since we are the client all output
 608          * actually goes to stderr.
 609          */
 610         log_init(av[0], options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
 611             SYSLOG_FACILITY_USER, 1);
 612
 613         /*
 614          * Read per-user configuration file.  Ignore the system wide config
 615          * file if the user specifies a config file on the command line.
 616          */
 617         if (config != NULL) {
 618                 if (!read_config_file(config, host, &options, 0))
 619                         fatal("Can't open user config file %.100s: "
 620                             "%.100s", config, strerror(errno));
 621         } else {
 622                 snprintf(buf, sizeof buf, "%.100s/%.100s", pw->pw_dir,
 623                     _PATH_SSH_USER_CONFFILE);
 624                 (void)read_config_file(buf, host, &options, 1);
 625
 626                 /* Read systemwide configuration file after use config. */
 627                 (void)read_config_file(_PATH_HOST_CONFIG_FILE, host,
 628                     &options, 0);
 629         }
 630
 631         /* Fill configuration defaults. */
 632         fill_default_options(&options);
 633
 634         channel_set_af(options.address_family);
 635
 636         /* reinit */
 637         log_init(av[0], options.log_level, SYSLOG_FACILITY_USER, 1);
 638
 639         seed_rng();
 640
 641         if (options.user == NULL)
 642                 options.user = xstrdup(pw->pw_name);
 643
 644         if (options.hostname != NULL)
 645                 host = options.hostname;
 646
 647         /* force lowercase for hostkey matching */
 648         if (options.host_key_alias != NULL) {
 649                 for (p = options.host_key_alias; *p; p++)
 650                         if (isupper(*p))
 651                                 *p = (char)tolower(*p);
 652         }
 653
 654         /* Get default port if port has not been set. */
 655         if (options.port == 0) {
 656                 sp = getservbyname(SSH_SERVICE_NAME, "tcp");
 657                 options.port = sp ? ntohs(sp->s_port) : SSH_DEFAULT_PORT;
 658         }
 659
 660         if (options.proxy_command != NULL &&
 661             strcmp(options.proxy_command, "none") == 0)
 662                 options.proxy_command = NULL;
 663         if (options.control_path != NULL &&
 664             strcmp(options.control_path, "none") == 0)
 665                 options.control_path = NULL;
 666
 667         if (options.control_path != NULL) {
 668                 char thishost[NI_MAXHOST];
 669
 670                 if (gethostname(thishost, sizeof(thishost)) == -1)
 671                         fatal("gethostname: %s", strerror(errno));
 672                 snprintf(buf, sizeof(buf), "%d", options.port);
 673                 cp = tilde_expand_filename(options.control_path,
 674                     original_real_uid);
 675                 options.control_path = percent_expand(cp, "p", buf, "h", host,
 676                     "r", options.user, "l", thishost, (char *)NULL);
 677                 xfree(cp);
 678         }
 679         if (mux_command != 0 && options.control_path == NULL)
 680                 fatal("No ControlPath specified for \"-O\" command");
 681         if (options.control_path != NULL)
 682                 control_client(options.control_path);
 683
 684         timeout_ms = options.connection_timeout * 1000;
 685
 686         /* Open a connection to the remote host. */
 687         if (ssh_connect(host, &hostaddr, options.port,
 688             options.address_family, options.connection_attempts, &timeout_ms,
 689             options.tcp_keep_alive,
 690 #ifdef HAVE_CYGWIN
 691             options.use_privileged_port,
 692 #else
 693             original_effective_uid == 0 && options.use_privileged_port,
 694 #endif
 695             options.proxy_command) != 0)
 696                 exit(255);
 697
 698         if (timeout_ms > 0)
 699                 debug3("timeout: %d ms remain after connect", timeout_ms);
 700
 701         /*
 702          * If we successfully made the connection, load the host private key
 703          * in case we will need it later for combined rsa-rhosts
 704          * authentication. This must be done before releasing extra
 705          * privileges, because the file is only readable by root.
 706          * If we cannot access the private keys, load the public keys
 707          * instead and try to execute the ssh-keysign helper instead.
 708          */
 709         sensitive_data.nkeys = 0;
 710         sensitive_data.keys = NULL;
 711         sensitive_data.external_keysign = 0;
 712         if (options.rhosts_rsa_authentication ||
 713             options.hostbased_authentication) {
 714                 sensitive_data.nkeys = 3;
 715                 sensitive_data.keys = xcalloc(sensitive_data.nkeys,
 716                     sizeof(Key));
 717
 718                 PRIV_START;
 719                 sensitive_data.keys[0] = key_load_private_type(KEY_RSA1,
 720                     _PATH_HOST_KEY_FILE, "", NULL, NULL);
 721                 sensitive_data.keys[1] = key_load_private_type(KEY_DSA,
 722                     _PATH_HOST_DSA_KEY_FILE, "", NULL, NULL);
 723                 sensitive_data.keys[2] = key_load_private_type(KEY_RSA,
 724                     _PATH_HOST_RSA_KEY_FILE, "", NULL, NULL);
 725                 PRIV_END;
 726
 727                 if (options.hostbased_authentication == 1 &&
 728                     sensitive_data.keys[0] == NULL &&
 729                     sensitive_data.keys[1] == NULL &&
 730                     sensitive_data.keys[2] == NULL) {
 731                         sensitive_data.keys[1] = key_load_public(
 732                             _PATH_HOST_DSA_KEY_FILE, NULL);
 733                         sensitive_data.keys[2] = key_load_public(
 734                             _PATH_HOST_RSA_KEY_FILE, NULL);
 735                         sensitive_data.external_keysign = 1;
 736                 }
 737         }
 738         /*
 739          * Get rid of any extra privileges that we may have.  We will no
 740          * longer need them.  Also, extra privileges could make it very hard
 741          * to read identity files and other non-world-readable files from the
 742          * user's home directory if it happens to be on a NFS volume where
 743          * root is mapped to nobody.
 744          */
 745         if (original_effective_uid == 0) {
 746                 PRIV_START;
 747                 permanently_set_uid(pw);
 748         }
 749
 750         /*
 751          * Now that we are back to our own permissions, create ~/.ssh
 752          * directory if it doesn't already exist.
 753          */
 754         snprintf(buf, sizeof buf, "%.100s%s%.100s", pw->pw_dir, strcmp(pw->pw_dir, "/") ? "/" : "", _PATH_SSH_USER_DIR);
 755         if (stat(buf, &st) < 0)
 756                 if (mkdir(buf, 0700) < 0)
 757                         error("Could not create directory '%.200s'.", buf);
 758
 759         /* load options.identity_files */
 760         load_public_identity_files();
 761
 762         /* Expand ~ in known host file names. */
 763         /* XXX mem-leaks: */
 764         options.system_hostfile =
 765             tilde_expand_filename(options.system_hostfile, original_real_uid);
 766         options.user_hostfile =
 767             tilde_expand_filename(options.user_hostfile, original_real_uid);
 768         options.system_hostfile2 =
 769             tilde_expand_filename(options.system_hostfile2, original_real_uid);
 770         options.user_hostfile2 =
 771             tilde_expand_filename(options.user_hostfile2, original_real_uid);
 772
 773         signal(SIGPIPE, SIG_IGN); /* ignore SIGPIPE early */
 774
 775         /* Log into the remote system.  This never returns if the login fails. */
 776         ssh_login(&sensitive_data, host, (struct sockaddr *)&hostaddr,
 777             pw, timeout_ms);
 778
 779         /* We no longer need the private host keys.  Clear them now. */
 780         if (sensitive_data.nkeys != 0) {
 781                 for (i = 0; i < sensitive_data.nkeys; i++) {
 782                         if (sensitive_data.keys[i] != NULL) {
 783                                 /* Destroys contents safely */
 784                                 debug3("clear hostkey %d", i);
 785                                 key_free(sensitive_data.keys[i]);
 786                                 sensitive_data.keys[i] = NULL;
 787                         }
 788                 }
 789                 xfree(sensitive_data.keys);
 790         }
 791         for (i = 0; i < options.num_identity_files; i++) {
 792                 if (options.identity_files[i]) {
 793                         xfree(options.identity_files[i]);
 794                         options.identity_files[i] = NULL;
 795                 }
 796                 if (options.identity_keys[i]) {
 797                         key_free(options.identity_keys[i]);
 798                         options.identity_keys[i] = NULL;
 799                 }
 800         }
 801
 802         exit_status = compat20 ? ssh_session2() : ssh_session();
 803         packet_close();
 804
 805         if (options.control_path != NULL && control_fd != -1)
 806                 unlink(options.control_path);
 807
 808         /*
 809          * Send SIGHUP to proxy command if used. We don't wait() in
 810          * case it hangs and instead rely on init to reap the child
 811          */
 812         if (proxy_command_pid > 1)
 813                 kill(proxy_command_pid, SIGHUP);
 814
 815         return exit_status;
 816 }
 817
 818 static void
 819 ssh_init_forwarding(void)
 820 {
 821         int success = 0;
 822         int i;
 823
 824         /* Initiate local TCP/IP port forwardings. */
 825         for (i = 0; i < options.num_local_forwards; i++) {
 826                 debug("Local connections to %.200s:%d forwarded to remote "
 827                     "address %.200s:%d",
 828                     (options.local_forwards[i].listen_host == NULL) ?
 829                     (options.gateway_ports ? "*" : "LOCALHOST") :
 830                     options.local_forwards[i].listen_host,
 831                     options.local_forwards[i].listen_port,
 832                     options.local_forwards[i].connect_host,
 833                     options.local_forwards[i].connect_port);
 834                 success += channel_setup_local_fwd_listener(
 835                     options.local_forwards[i].listen_host,
 836                     options.local_forwards[i].listen_port,
 837                     options.local_forwards[i].connect_host,
 838                     options.local_forwards[i].connect_port,
 839                     options.gateway_ports);
 840         }
 841         if (i > 0 && success != i && options.exit_on_forward_failure)
 842                 fatal("Could not request local forwarding.");
 843         if (i > 0 && success == 0)
 844                 error("Could not request local forwarding.");
 845
 846         /* Initiate remote TCP/IP port forwardings. */
 847         for (i = 0; i < options.num_remote_forwards; i++) {
 848                 debug("Remote connections from %.200s:%d forwarded to "
 849                     "local address %.200s:%d",
 850                     (options.remote_forwards[i].listen_host == NULL) ?
 851                     "LOCALHOST" : options.remote_forwards[i].listen_host,
 852                     options.remote_forwards[i].listen_port,
 853                     options.remote_forwards[i].connect_host,
 854                     options.remote_forwards[i].connect_port);
 855                 if (channel_request_remote_forwarding(
 856                     options.remote_forwards[i].listen_host,
 857                     options.remote_forwards[i].listen_port,
 858                     options.remote_forwards[i].connect_host,
 859                     options.remote_forwards[i].connect_port) < 0) {
 860                         if (options.exit_on_forward_failure)
 861                                 fatal("Could not request remote forwarding.");
 862                         else
 863                                 logit("Warning: Could not request remote "
 864                                     "forwarding.");
 865                 }
 866         }
 867
 868         /* Initiate tunnel forwarding. */
 869         if (options.tun_open != SSH_TUNMODE_NO) {
 870                 if (client_request_tun_fwd(options.tun_open,
 871                     options.tun_local, options.tun_remote) == -1) {
 872                         if (options.exit_on_forward_failure)
 873                                 fatal("Could not request tunnel forwarding.");
 874                         else
 875                                 error("Could not request tunnel forwarding.");
 876                 }
 877         }
 878 }
 879
 880 static void
 881 check_agent_present(void)
 882 {
 883         if (options.forward_agent) {
 884                 /* Clear agent forwarding if we don't have an agent. */
 885                 if (!ssh_agent_present())
 886                         options.forward_agent = 0;
 887         }
 888 }
 889
 890 static int
 891 ssh_session(void)
 892 {
 893         int type;
 894         int interactive = 0;
 895         int have_tty = 0;
 896         struct winsize ws;
 897         char *cp;
 898         const char *display;
 899
 900         /* Enable compression if requested. */
 901         if (options.compression) {
 902                 debug("Requesting compression at level %d.", options.compression_level);
 903
 904                 if (options.compression_level < 1 || options.compression_level > 9)
 905                         fatal("Compression level must be from 1 (fast) to 9 (slow, best).");
 906
 907                 /* Send the request. */
 908                 packet_start(SSH_CMSG_REQUEST_COMPRESSION);
 909                 packet_put_int(options.compression_level);
 910                 packet_send();
 911                 packet_write_wait();
 912                 type = packet_read();
 913                 if (type == SSH_SMSG_SUCCESS)
 914                         packet_start_compression(options.compression_level);
 915                 else if (type == SSH_SMSG_FAILURE)
 916                         logit("Warning: Remote host refused compression.");
 917                 else
 918                         packet_disconnect("Protocol error waiting for compression response.");
 919         }
 920         /* Allocate a pseudo tty if appropriate. */
 921         if (tty_flag) {
 922                 debug("Requesting pty.");
 923
 924                 /* Start the packet. */
 925                 packet_start(SSH_CMSG_REQUEST_PTY);
 926
 927                 /* Store TERM in the packet.  There is no limit on the
 928                    length of the string. */
 929                 cp = getenv("TERM");
 930                 if (!cp)
 931                         cp = "";
 932                 packet_put_cstring(cp);
 933
 934                 /* Store window size in the packet. */
 935                 if (ioctl(fileno(stdin), TIOCGWINSZ, &ws) < 0)
 936                         memset(&ws, 0, sizeof(ws));
 937                 packet_put_int((u_int)ws.ws_row);
 938                 packet_put_int((u_int)ws.ws_col);
 939                 packet_put_int((u_int)ws.ws_xpixel);
 940                 packet_put_int((u_int)ws.ws_ypixel);
 941
 942                 /* Store tty modes in the packet. */
 943                 tty_make_modes(fileno(stdin), NULL);
 944
 945                 /* Send the packet, and wait for it to leave. */
 946                 packet_send();
 947                 packet_write_wait();
 948
 949                 /* Read response from the server. */
 950                 type = packet_read();
 951                 if (type == SSH_SMSG_SUCCESS) {
 952                         interactive = 1;
 953                         have_tty = 1;
 954                 } else if (type == SSH_SMSG_FAILURE)
 955                         logit("Warning: Remote host failed or refused to allocate a pseudo tty.");
 956                 else
 957                         packet_disconnect("Protocol error waiting for pty request response.");
 958         }
 959         /* Request X11 forwarding if enabled and DISPLAY is set. */
 960         display = getenv("DISPLAY");
 961         if (options.forward_x11 && display != NULL) {
 962                 char *proto, *data;
 963                 /* Get reasonable local authentication information. */
 964                 client_x11_get_proto(display, options.xauth_location,
 965                     options.forward_x11_trusted, &proto, &data);
 966                 /* Request forwarding with authentication spoofing. */
 967                 debug("Requesting X11 forwarding with authentication spoofing.");
 968                 x11_request_forwarding_with_spoofing(0, display, proto, data);
 969
 970                 /* Read response from the server. */
 971                 type = packet_read();
 972                 if (type == SSH_SMSG_SUCCESS) {
 973                         interactive = 1;
 974                 } else if (type == SSH_SMSG_FAILURE) {
 975                         logit("Warning: Remote host denied X11 forwarding.");
 976                 } else {
 977                         packet_disconnect("Protocol error waiting for X11 forwarding");
 978                 }
 979         }
 980         /* Tell the packet module whether this is an interactive session. */
 981         packet_set_interactive(interactive);
 982
 983         /* Request authentication agent forwarding if appropriate. */
 984         check_agent_present();
 985
 986         if (options.forward_agent) {
 987                 debug("Requesting authentication agent forwarding.");
 988                 auth_request_forwarding();
 989
 990                 /* Read response from the server. */
 991                 type = packet_read();
 992                 packet_check_eom();
 993                 if (type != SSH_SMSG_SUCCESS)
 994                         logit("Warning: Remote host denied authentication agent forwarding.");
 995         }
 996
 997         /* Initiate port forwardings. */
 998         ssh_init_forwarding();
 999
1000         /* If requested, let ssh continue in the background. */
1001         if (fork_after_authentication_flag)
1002                 if (daemon(1, 1) < 0)
1003                         fatal("daemon() failed: %.200s", strerror(errno));
1004
1005         /*
1006          * If a command was specified on the command line, execute the
1007          * command now. Otherwise request the server to start a shell.
1008          */
1009         if (buffer_len(&command) > 0) {
1010                 int len = buffer_len(&command);
1011                 if (len > 900)
1012                         len = 900;
1013                 debug("Sending command: %.*s", len, (u_char *)buffer_ptr(&command));
1014                 packet_start(SSH_CMSG_EXEC_CMD);
1015                 packet_put_string(buffer_ptr(&command), buffer_len(&command));
1016                 packet_send();
1017                 packet_write_wait();
1018         } else {
1019                 debug("Requesting shell.");
1020                 packet_start(SSH_CMSG_EXEC_SHELL);
1021                 packet_send();
1022                 packet_write_wait();
1023         }
1024
1025         /* Enter the interactive session. */
1026         return client_loop(have_tty, tty_flag ?
1027             options.escape_char : SSH_ESCAPECHAR_NONE, 0);
1028 }
1029
1030 static void
1031 ssh_subsystem_reply(int type, u_int32_t seq, void *ctxt)
1032 {
1033         int id, len;
1034
1035         id = packet_get_int();
1036         len = buffer_len(&command);
1037         if (len > 900)
1038                 len = 900;
1039         packet_check_eom();
1040         if (type == SSH2_MSG_CHANNEL_FAILURE)
1041                 fatal("Request for subsystem '%.*s' failed on channel %d",
1042                     len, (u_char *)buffer_ptr(&command), id);
1043 }
1044
1045 void
1046 client_global_request_reply_fwd(int type, u_int32_t seq, void *ctxt)
1047 {
1048         int i;
1049
1050         i = client_global_request_id++;
1051         if (i >= options.num_remote_forwards)
1052                 return;
1053         debug("remote forward %s for: listen %d, connect %s:%d",
1054             type == SSH2_MSG_REQUEST_SUCCESS ? "success" : "failure",
1055             options.remote_forwards[i].listen_port,
1056             options.remote_forwards[i].connect_host,
1057             options.remote_forwards[i].connect_port);
1058         if (type == SSH2_MSG_REQUEST_FAILURE) {
1059                 if (options.exit_on_forward_failure)
1060                         fatal("Error: remote port forwarding failed for "
1061                             "listen port %d",
1062                             options.remote_forwards[i].listen_port);
1063                 else
1064                         logit("Warning: remote port forwarding failed for "
1065                             "listen port %d",
1066                             options.remote_forwards[i].listen_port);
1067         }
1068 }
1069
1070 static void
1071 ssh_control_listener(void)
1072 {
1073         struct sockaddr_un addr;
1074         mode_t old_umask;
1075         int addr_len;
1076
1077         if (options.control_path == NULL ||
1078             options.control_master == SSHCTL_MASTER_NO)
1079                 return;
1080
1081         debug("setting up multiplex master socket");
1082
1083         memset(&addr, '\0', sizeof(addr));
1084         addr.sun_family = AF_UNIX;
1085         addr_len = offsetof(struct sockaddr_un, sun_path) +
1086             strlen(options.control_path) + 1;
1087
1088         if (strlcpy(addr.sun_path, options.control_path,
1089             sizeof(addr.sun_path)) >= sizeof(addr.sun_path))
1090                 fatal("ControlPath too long");
1091
1092         if ((control_fd = socket(PF_UNIX, SOCK_STREAM, 0)) < 0)
1093                 fatal("%s socket(): %s", __func__, strerror(errno));
1094
1095         old_umask = umask(0177);
1096         if (bind(control_fd, (struct sockaddr *)&addr, addr_len) == -1) {
1097                 control_fd = -1;
1098                 if (errno == EINVAL || errno == EADDRINUSE)
1099                         fatal("ControlSocket %s already exists",
1100                             options.control_path);
1101                 else
1102                         fatal("%s bind(): %s", __func__, strerror(errno));
1103         }
1104         umask(old_umask);
1105
1106         if (listen(control_fd, 64) == -1)
1107                 fatal("%s listen(): %s", __func__, strerror(errno));
1108
1109         set_nonblock(control_fd);
1110 }
1111
1112 /* request pty/x11/agent/tcpfwd/shell for channel */
1113 static void
1114 ssh_session2_setup(int id, void *arg)
1115 {
1116         extern char **environ;
1117         const char *display;
1118         int interactive = tty_flag;
1119
1120         display = getenv("DISPLAY");
1121         if (options.forward_x11 && display != NULL) {
1122                 char *proto, *data;
1123                 /* Get reasonable local authentication information. */
1124                 client_x11_get_proto(display, options.xauth_location,
1125                     options.forward_x11_trusted, &proto, &data);
1126                 /* Request forwarding with authentication spoofing. */
1127                 debug("Requesting X11 forwarding with authentication spoofing.");
1128                 x11_request_forwarding_with_spoofing(id, display, proto, data);
1129                 interactive = 1;
1130                 /* XXX wait for reply */
1131         }
1132
1133         check_agent_present();
1134         if (options.forward_agent) {
1135                 debug("Requesting authentication agent forwarding.");
1136                 channel_request_start(id, "auth-agent-req@openssh.com", 0);
1137                 packet_send();
1138         }
1139
1140         client_session2_setup(id, tty_flag, subsystem_flag, getenv("TERM"),
1141             NULL, fileno(stdin), &command, environ, &ssh_subsystem_reply);
1142
1143         packet_set_interactive(interactive);
1144 }
1145
1146 /* open new channel for a session */
1147 static int
1148 ssh_session2_open(void)
1149 {
1150         Channel *c;
1151         int window, packetmax, in, out, err;
1152
1153         if (stdin_null_flag) {
1154                 in = open(_PATH_DEVNULL, O_RDONLY);
1155         } else {
1156                 in = dup(STDIN_FILENO);
1157         }
1158         out = dup(STDOUT_FILENO);
1159         err = dup(STDERR_FILENO);
1160
1161         if (in < 0 || out < 0 || err < 0)
1162                 fatal("dup() in/out/err failed");
1163
1164         /* enable nonblocking unless tty */
1165         if (!isatty(in))
1166                 set_nonblock(in);
1167         if (!isatty(out))
1168                 set_nonblock(out);
1169         if (!isatty(err))
1170                 set_nonblock(err);
1171
1172         window = CHAN_SES_WINDOW_DEFAULT;
1173         packetmax = CHAN_SES_PACKET_DEFAULT;
1174         if (tty_flag) {
1175                 window >>= 1;
1176                 packetmax >>= 1;
1177         }
1178         c = channel_new(
1179             "session", SSH_CHANNEL_OPENING, in, out, err,
1180             window, packetmax, CHAN_EXTENDED_WRITE,
1181             "client-session", /*nonblock*/0);
1182
1183         debug3("ssh_session2_open: channel_new: %d", c->self);
1184
1185         channel_send_open(c->self);
1186         if (!no_shell_flag)
1187                 channel_register_confirm(c->self, ssh_session2_setup, NULL);
1188
1189         return c->self;
1190 }
1191
1192 static int
1193 ssh_session2(void)
1194 {
1195         int id = -1;
1196
1197         /* XXX should be pre-session */
1198         ssh_init_forwarding();
1199
1200         if (!no_shell_flag || (datafellows & SSH_BUG_DUMMYCHAN))
1201                 id = ssh_session2_open();
1202
1203         /* Execute a local command */
1204         if (options.local_command != NULL &&
1205             options.permit_local_command)
1206                 ssh_local_cmd(options.local_command);
1207
1208         /* Start listening for multiplex clients */
1209         ssh_control_listener();
1210
1211         /* If requested, let ssh continue in the background. */
1212         if (fork_after_authentication_flag)
1213                 if (daemon(1, 1) < 0)
1214                         fatal("daemon() failed: %.200s", strerror(errno));
1215
1216         return client_loop(tty_flag, tty_flag ?
1217             options.escape_char : SSH_ESCAPECHAR_NONE, id);
1218 }
1219
1220 static void
1221 load_public_identity_files(void)
1222 {
1223         char *filename, *cp, thishost[NI_MAXHOST];
1224         int i = 0;
1225         Key *public;
1226         struct passwd *pw;
1227 #ifdef SMARTCARD
1228         Key **keys;
1229
1230         if (options.smartcard_device != NULL &&
1231             options.num_identity_files < SSH_MAX_IDENTITY_FILES &&
1232             (keys = sc_get_keys(options.smartcard_device, NULL)) != NULL) {
1233                 int count = 0;
1234                 for (i = 0; keys[i] != NULL; i++) {
1235                         count++;
1236                         memmove(&options.identity_files[1], &options.identity_files[0],
1237                             sizeof(char *) * (SSH_MAX_IDENTITY_FILES - 1));
1238                         memmove(&options.identity_keys[1], &options.identity_keys[0],
1239                             sizeof(Key *) * (SSH_MAX_IDENTITY_FILES - 1));
1240                         options.num_identity_files++;
1241                         options.identity_keys[0] = keys[i];
1242                         options.identity_files[0] = sc_get_key_label(keys[i]);
1243                 }
1244                 if (options.num_identity_files > SSH_MAX_IDENTITY_FILES)
1245                         options.num_identity_files = SSH_MAX_IDENTITY_FILES;
1246                 i = count;
1247                 xfree(keys);
1248         }
1249 #endif /* SMARTCARD */
1250         if ((pw = getpwuid(original_real_uid)) == NULL)
1251                 fatal("load_public_identity_files: getpwuid failed");
1252         if (gethostname(thishost, sizeof(thishost)) == -1)
1253                 fatal("load_public_identity_files: gethostname: %s",
1254                     strerror(errno));
1255         for (; i < options.num_identity_files; i++) {
1256                 cp = tilde_expand_filename(options.identity_files[i],
1257                     original_real_uid);
1258                 filename = percent_expand(cp, "d", pw->pw_dir,
1259                     "u", pw->pw_name, "l", thishost, "h", host,
1260                     "r", options.user, (char *)NULL);
1261                 xfree(cp);
1262                 public = key_load_public(filename, NULL);
1263                 debug("identity file %s type %d", filename,
1264                     public ? public->type : -1);
1265                 xfree(options.identity_files[i]);
1266                 options.identity_files[i] = filename;
1267                 options.identity_keys[i] = public;
1268         }
1269 }
1270
1271 static void
1272 control_client_sighandler(int signo)
1273 {
1274         control_client_terminate = signo;
1275 }
1276
1277 static void
1278 control_client_sigrelay(int signo)
1279 {
1280         if (control_server_pid > 1)
1281                 kill(control_server_pid, signo);
1282 }
1283
1284 static int
1285 env_permitted(char *env)
1286 {
1287         int i, ret;
1288         char name[1024], *cp;
1289
1290         if ((cp = strchr(env, '=')) == NULL || cp == env)
1291                 return (0);
1292         ret = snprintf(name, sizeof(name), "%.*s", (int)(cp - env), env);
1293         if (ret <= 0 || (size_t)ret >= sizeof(name))
1294                 fatal("env_permitted: name '%.100s...' too long", env);
1295
1296         for (i = 0; i < options.num_send_env; i++)
1297                 if (match_pattern(name, options.send_env[i]))
1298                         return (1);
1299
1300         return (0);
1301 }
1302
1303 static void
1304 control_client(const char *path)
1305 {
1306         struct sockaddr_un addr;
1307         int i, r, fd, sock, exitval[2], num_env, addr_len;
1308         Buffer m;
1309         char *term;
1310         extern char **environ;
1311         u_int  flags;
1312
1313         if (mux_command == 0)
1314                 mux_command = SSHMUX_COMMAND_OPEN;
1315
1316         switch (options.control_master) {
1317         case SSHCTL_MASTER_AUTO:
1318         case SSHCTL_MASTER_AUTO_ASK:
1319                 debug("auto-mux: Trying existing master");
1320                 /* FALLTHROUGH */
1321         case SSHCTL_MASTER_NO:
1322                 break;
1323         default:
1324                 return;
1325         }
1326
1327         memset(&addr, '\0', sizeof(addr));
1328         addr.sun_family = AF_UNIX;
1329         addr_len = offsetof(struct sockaddr_un, sun_path) +
1330             strlen(path) + 1;
1331
1332         if (strlcpy(addr.sun_path, path,
1333             sizeof(addr.sun_path)) >= sizeof(addr.sun_path))
1334                 fatal("ControlPath too long");
1335
1336         if ((sock = socket(PF_UNIX, SOCK_STREAM, 0)) < 0)
1337                 fatal("%s socket(): %s", __func__, strerror(errno));
1338
1339         if (connect(sock, (struct sockaddr *)&addr, addr_len) == -1) {
1340                 if (mux_command != SSHMUX_COMMAND_OPEN) {
1341                         fatal("Control socket connect(%.100s): %s", path,
1342                             strerror(errno));
1343                 }
1344                 if (errno == ENOENT)
1345                         debug("Control socket \"%.100s\" does not exist", path);
1346                 else {
1347                         error("Control socket connect(%.100s): %s", path,
1348                             strerror(errno));
1349                 }
1350                 close(sock);
1351                 return;
1352         }
1353
1354         if (stdin_null_flag) {
1355                 if ((fd = open(_PATH_DEVNULL, O_RDONLY)) == -1)
1356                         fatal("open(/dev/null): %s", strerror(errno));
1357                 if (dup2(fd, STDIN_FILENO) == -1)
1358                         fatal("dup2: %s", strerror(errno));
1359                 if (fd > STDERR_FILENO)
1360                         close(fd);
1361         }
1362
1363         term = getenv("TERM");
1364
1365         flags = 0;
1366         if (tty_flag)
1367                 flags |= SSHMUX_FLAG_TTY;
1368         if (subsystem_flag)
1369                 flags |= SSHMUX_FLAG_SUBSYS;
1370         if (options.forward_x11)
1371                 flags |= SSHMUX_FLAG_X11_FWD;
1372         if (options.forward_agent)
1373                 flags |= SSHMUX_FLAG_AGENT_FWD;
1374
1375         buffer_init(&m);
1376
1377         /* Send our command to server */
1378         buffer_put_int(&m, mux_command);
1379         buffer_put_int(&m, flags);
1380         if (ssh_msg_send(sock, SSHMUX_VER, &m) == -1)
1381                 fatal("%s: msg_send", __func__);
1382         buffer_clear(&m);
1383
1384         /* Get authorisation status and PID of controlee */
1385         if (ssh_msg_recv(sock, &m) == -1)
1386                 fatal("%s: msg_recv", __func__);
1387         if (buffer_get_char(&m) != SSHMUX_VER)
1388                 fatal("%s: wrong version", __func__);
1389         if (buffer_get_int(&m) != 1)
1390                 fatal("Connection to master denied");
1391         control_server_pid = buffer_get_int(&m);
1392
1393         buffer_clear(&m);
1394
1395         switch (mux_command) {
1396         case SSHMUX_COMMAND_ALIVE_CHECK:
1397                 fprintf(stderr, "Master running (pid=%d)\r\n",
1398                     control_server_pid);
1399                 exit(0);
1400         case SSHMUX_COMMAND_TERMINATE:
1401                 fprintf(stderr, "Exit request sent.\r\n");
1402                 exit(0);
1403         case SSHMUX_COMMAND_OPEN:
1404                 /* continue below */
1405                 break;
1406         default:
1407                 fatal("silly mux_command %d", mux_command);
1408         }
1409
1410         /* SSHMUX_COMMAND_OPEN */
1411         buffer_put_cstring(&m, term ? term : "");
1412         buffer_append(&command, "\0", 1);
1413         buffer_put_cstring(&m, buffer_ptr(&command));
1414
1415         if (options.num_send_env == 0 || environ == NULL) {
1416                 buffer_put_int(&m, 0);
1417         } else {
1418                 /* Pass environment */
1419                 num_env = 0;
1420                 for (i = 0; environ[i] != NULL; i++)
1421                         if (env_permitted(environ[i]))
1422                                 num_env++; /* Count */
1423
1424                 buffer_put_int(&m, num_env);
1425
1426                 for (i = 0; environ[i] != NULL && num_env >= 0; i++)
1427                         if (env_permitted(environ[i])) {
1428                                 num_env--;
1429                                 buffer_put_cstring(&m, environ[i]);
1430                         }
1431         }
1432
1433         if (ssh_msg_send(sock, SSHMUX_VER, &m) == -1)
1434                 fatal("%s: msg_send", __func__);
1435
1436         if (mm_send_fd(sock, STDIN_FILENO) == -1 ||
1437             mm_send_fd(sock, STDOUT_FILENO) == -1 ||
1438             mm_send_fd(sock, STDERR_FILENO) == -1)
1439                 fatal("%s: send fds failed", __func__);
1440
1441         /* Wait for reply, so master has a chance to gather ttymodes */
1442         buffer_clear(&m);
1443         if (ssh_msg_recv(sock, &m) == -1)
1444                 fatal("%s: msg_recv", __func__);
1445         if (buffer_get_char(&m) != SSHMUX_VER)
1446                 fatal("%s: wrong version", __func__);
1447         buffer_free(&m);
1448
1449         signal(SIGHUP, control_client_sighandler);
1450         signal(SIGINT, control_client_sighandler);
1451         signal(SIGTERM, control_client_sighandler);
1452         signal(SIGWINCH, control_client_sigrelay);
1453
1454         if (tty_flag)
1455                 enter_raw_mode();
1456
1457         /*
1458          * Stick around until the controlee closes the client_fd.
1459          * Before it does, it is expected to write this process' exit
1460          * value (one int). This process must read the value and wait for
1461          * the closure of the client_fd; if this one closes early, the
1462          * multiplex master will terminate early too (possibly losing data).
1463          */
1464         exitval[0] = 0;
1465         for (i = 0; !control_client_terminate && i < (int)sizeof(exitval);) {
1466                 r = read(sock, (char *)exitval + i, sizeof(exitval) - i);
1467                 if (r == 0) {
1468                         debug2("Received EOF from master");
1469                         break;
1470                 }
1471                 if (r == -1) {
1472                         if (errno == EINTR)
1473                                 continue;
1474                         fatal("%s: read %s", __func__, strerror(errno));
1475                 }
1476                 i += r;
1477         }
1478
1479         close(sock);
1480         leave_raw_mode();
1481         if (i > (int)sizeof(int))
1482                 fatal("%s: master returned too much data (%d > %lu)",
1483                     __func__, i, sizeof(int));
1484         if (control_client_terminate) {
1485                 debug2("Exiting on signal %d", control_client_terminate);
1486                 exitval[0] = 255;
1487         } else if (i < (int)sizeof(int)) {
1488                 debug2("Control master terminated unexpectedly");
1489                 exitval[0] = 255;
1490         } else
1491                 debug2("Received exit status from master %d", exitval[0]);
1492
1493         if (tty_flag && options.log_level != SYSLOG_LEVEL_QUIET)
1494                 fprintf(stderr, "Shared connection to %s closed.\r\n", host);
1495
1496         exit(exitval[0]);
1497 }